A different motivation to study eTFF's is related to physics beyond the standard model.
The results from measurements of the muon \((g-2)\)  differ w.r.t. the Standard Model predictions [1]}, [2]}.
It appears that the eTFF's of light pseudo-scalar mesons enter in the hadronic light-by-light scattering calculation and, together with the vacuum polarization, are currently the most prominent part of systematic uncertainties of Standard Model predictions ([3]}).
Furthermore, Dalitz decays constitute an irreducible background in searches for a possibly existing dark photon, an extra U(1) gauge boson which mediates the interaction between Standard Model photons and dark matter.
Several measurement were performed searching for signals from a two-body decay of the dark photon in meson and baryon Dalitz-decays and in heavy-ion collisions with negative outcome but providing important limits on its coupling strength to the SM photon (see [4]} for further information).
